Vous pouvez essayer l'agrégation ci-dessous, mais je ne vous recommanderai pas de l'utiliser avec le grand ensemble de données.
db.collection.aggregate([
{ "$match": {
"date" : {
"$gte": new ISODate("2018-09-01T00:00:00.000Z"),
"$lte": new ISODate("2018-09-12T23:59:59.000Z")
}
}},
{ "$unwind": "$reading" },
{ "$sort": { "date": -1 }},
{ "$group": { "_id": null, "data": { "$push": "$$ROOT" }}},
{ "$project": {
"data": {
"$filter": {
"input": {
"$map": {
"input": { "$range": [0, { "$size": "$data" }] },
"as": "tt",
"in": {
"$let": {
"vars": {
"first": { "$arrayElemAt": ["$data", "$$tt"] },
"second": { "$arrayElemAt": ["$data", { "$add": ["$$tt", 1] }] }
},
"in": {
"currentWeight": "$$first.reading.weight.measurement",
"weightDifference": { "$subtract": ["$$second.reading.weight.measurement", "$$first.reading.weight.measurement"] },
"_id": "$$first._id",
"date": "$$first.date"
}
}
}
}
},
"cond": { "$ne": ["$$this.weightDifference", null] }
}
}
}
},
{ "$unwind": "$data" },
{ "$replaceRoot": { "newRoot": "$data" }}
])
